Magnetron



United rates Fee 3,078,387 MAGNETRON Eduard G. Dorgelo, Huntington,N.Y., assignor to North American Philips Company, Inc., New York, N.Y.,a corporation of Delaware Filed Sept. 8, 1960, Ser. No. 54,763 6 Claims.(Cl. 315-39.'75)

My invention relates to magnetrons. More particularly, the inventionrelates to magnetrons employing a radially mounted cathode and externalmagnets and includes means for improving the vacuum inside the mag.-netron under operating conditions.

The invention will be described in connection with the accompanyingdrawing which shows a magnetron according to the invention.

The magnetron shown in the drawing is of the radial. cathode typeemploying external magnets 1, 2. The cathode 3 is supported within ahollow anode block 4 by lead-in conductors 5 and 6 sealed through glassseals 7 and 8 mounted at outer ends of pipes 9 and 10 hermetical- 1yfastened within the walls of the block 4.

Anode block 4 is provided with a plurality of slots 11 and 12 concentricwith the cathode such that when the device is energized, oscillationsare set up therein. These oscillations may be led out of the tube bymeans of a coupling loop which extends into one of the cylindricalopenings 11 and extends into and is hermetically sealed in a pipe 13.

Discs 14 and 15 constituted of a getter material such as zirconium ortitanium are provided on both ends of the cathode spaced from the Wallsof block 4 by at least several millimeters. Stray electrons penetratinginto the spaces 17 and 18 between the discs 14 and 15 and the block 1will be spiralled by the axial magnetic field providing in this way anenhanced probability to ionize residual gas particles.

Since there exists also in spaces 17 and 18 an axial D.-C. field,because of the D.-C. potential applied between the anode and cathode,these positive ions will be accelerated toward the discs or end shields14 and 15 and absorbed there by getter action.

This tube can be considered, therefore, as having two built-in ionpumps.

It is essential only that the external surfaces of the end shields becovered with gettering material in order to attract the ions. Goodresults are obtained, for example, by using molybdenum caps covered withzirconium or titanium powder.

It is not necessary for good results to operate with the end shields atelevated temperatures. In fact, best results are obtained when theseshields are in poor thermal contact with the hot cathode.

Furthermore, where some end emission is desired, the internal surfacesof the end caps should not be coated with materials such as zirconium ortitanium.

The tube in accordance with the invention has a materially shortenedrequired aging time, i.e. the time required to exhaust the tube beforeit is ready for operation. Typical tubes according to the invention havean aging time which is approximately 20% of that of comparable tubes notmade in accordance with the invention.

The fore-going embodiment is illustrative only, the invention beingdefined by the appended claims which should be construed as broadly aspossible in view of the art.

What I claim is:

1. An electron discharge tube comprising a hollow anode block forproducing a D.-C. field and having a plurality of slots in whichoscillations can occur, a cathode disposed within said anode blockconcentric with said slots, field 3,078,387 Patented Feb. 19, 1963 "iceproducing means external to said anode block for producing a magneticfield coaxial with the cathode, and end shield members adjacent the endsof said cathode between said cathode and said anode block and spacedfrom said anode block, said end shield members having at least surfaceportions thereof constituted of a material adapted to absorb residualgases ionized by the D.-C. field.

2. An electron discharge tube comprising a hollow anode block forproducing a D.-C. field and having a plurality of cylindrical openingsin which oscillations can occur, a cathode disposed within said anodeblock concentric with said slots, field-producing means external to saidanode block for producing a magnetic field coaxial with the cathode, andend shield members positioned at the ends of said cathode and spacedfrom said anode block,

the external surfaces of said end shield members being constituted of amaterial adapted to absorb residual gases ionized by the D.-C. field.

3. An electron discharge tube comprising a hollow anode block theproducing a 11-0. field and having a plurality of slots in whichoscillations can occur, a cathode disposed within said block concentricwith said slots, field producing means external to said anode block forproducing a magnetic field coaxial with said cathode, and end at iieldmembers positioned at the ends of said cathode and spaced from saidanode block, said end shield members being constituted of refractorymetal covered on the external surfaces only with a material which isadapted to .absorb residual gases ionized by the D.-C. field.

4. An electron discharge tube comprising a hollow anode block forproducing a D.-C. field and having a plurality of slots in whichoscillations can occur, a cathode disposed Within said block concentricwith said slots, fieldproducing means external to said anode block forproducing a magnetic field coaxial with said cathode, and end shieldmembers positioned at the ends of said cathode and spaced from the anodeblock, said end shield members being constituted of molybdenum, theexternal surfaces only of said end shield members being covered with amaterial which is adapted to absorb residual gases ionized by the D.-C.field.

5. An electron discharge tube comprising a hollow anode block forproducing a D.-C. field and having a plurality of slots in whichoscillations can occur, a cathode disposed within said anode blockconcentric with said slots, field-producing means external to said anodeblock for producing a magnetic field coaxial with the cathode, and endshield members positioned at the ends of said cathode and spaced fromsaid anode block, said end shield members being constituted ofmolybdenum, the external surfaces only of said end shield members beingcovered with zirconium for absorbing residual gases ionized by the D.-C.field.

6. An electron discharge tube comprising a hollow anode block forproducing a D.-C. field and having a plurality of slots in whichoscillations can occur, a cathode disposed within said block concentricwith said slots, field- References Cited in the file of this patentUNITED STATES PATENTS 2,410,396 Spencer Oct. 29, 1946 2,445,447 MartinJuly 20, 1948 2,960,618 Waer Nov. 15, 1960.

1. AN ELECTRON DISCHARGE TUBE COMPRISING A HOLLOW ANODE BLOCK FORPRODUCING A D.-C. FIELD AND HAVING A PLURALITY OF SLOTS IN WHICHOSCILLATIONS CAN OCCUR, A CATHODE DISPOSED WITHIN SAID ANODE BLOCKCONCENTRIC WITH SAID SLOTS, FIELD PRODUCING MEANS EXTERNAL TO SAID ANODEBLOCK FOR PRODUCING A MAGNETIC FIELD COAXIAL WITH THE CATHODE, AND ENDSHIELD MEMBERS ADJACENT THE ENDS OF SAID CATHODE BETWEEN SAID CATHODEAND SAID ANODE BLOCK AND SPACED FROM SAID ANODE BLOCK, SAID END SHIELDMEMBERS HAVING AT LEAST SURFACE PORTIONS THEREOF CONSTITUTED OF AMATERIAL ADAPTED TO ABSORB RESIDUAL GASES IONIZED BY THE D.-C. FIELD.